The synthesis of 3,3'-diaminobenzidine hereinafter DAB by the ammonolysis of 3,3'-dichlorobenzidine, hereinafter DCB, is known in the art as described in French patent No. 1,475,631 (1967). Unfortunately, the above and other prior processes suffer from a number of disadvantages such as the resultant impure reaction products which comprise DAB, DCB, and catalysts when such are employed in the synthesis.